Fuze for small caliber ammunition



Feb. 25, 1958 J. PlsKoRsKl ET AL FUZE FOR SMALL CALIBER AMMUNITION Filed NOV. 6, 1953 mi@ .m mkrm mmm f WMP. fw. :..m P M wm ,u @5 i y BM J. f.

24,5% Patented Feb. 25, 1958 FUZE FOR SMALL CALIBER AMIVIUNITION John Piskorski and Selim S. Podnos, Washington, D. C., assignors to the United States of America as represented by the Secretary of the Arn'ifgJ Application November 6, 1953, Serial No. 390,7 63

4 Claims. (Cl. 102-79) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to us of any royalty there- This invention relates to a delayed arming mechanism for projectile fuzes and more particularly to safety fuzes of the spherical rotor type.

An object of the invention is to provide a fuze for a projectile which may be red from a gun in an unarmed position, but which will become armed after the projectile leaves the gun, the time of arming being controlled by the design of the sperical rotor and the safety spring.

Another object of the invention is to provide a fuse which increases protection against premature functioning, when passing through objects such as leaves, camouilage, rain drops and the like, but will cause instantaneous detonation upon intended point contact.

A further object of the invention is the provision of passage means of such construction as will result in the firing pin engaging the detonator with a greater force than heretofore attained by a fuze of this character.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which is illustrated a preferred one of the various possible embodiments of the invention:

Figure 1 is a longitudinal section of the fuze, showing the parts in an unarmed or safe position;

Figure 2 is a fragmentary view similar to Figure 1, showing the parts in anl armed condition;

Figure 3 is a cross section view taken along the line 3-3 of Figure 1.

Figure 4 is a perspective view of the rotor safety spring.

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

This invention is an improvement upon the construction shown in U. S. Patent 2,495,432, issued lanuary 24, 1950 to P. H. Thompson. t is especially adapted for use in connection with ammunition of small caliber, i. e. mm., because it effectively utilizes the small amount of space within which the elements of the invention may be housed. However, it is also applicable to ammunition of medium and large calibers.

Referring now more particularly to Figure l there is shown a tapered fuze body l which is threaded as at 3 for attachment to the nose of a projectile 4. The body has a cylindrical bore 5 extending from the rear end into the forward section of the body'and terminating in a hemispherical forward end e. Extending from the center of this hemispherical portion to the forward end of the fuze body is a co-axial second bore 7 of reduced diameter, which is forwardly and outwardly tapered.

Closely tting overthe tapered fuze body is a tapered shield or cover 8 having a rounded, closed cap 9 spaced from the forward end of the second bore 7. At its base the cover 3 is spun over to form a crimp as indicated at i0 in Figure l.

The interior of the rearward portion of the bore 5 is threaded as at il to screW-threadedly receive a cylindrical housing 12 having a hollow interior for receiving a booster charge i3 held therein by crimping as indicated at 13a. Extending forward from the booster charge is a short ash passage 1d. This passage opens into a forwardly opening cup shaped depression 15. The two surfaces 6 and l5 jointly define a spherical seat which receives with a smooth fit, an essentially spherical rotor 16.

The rotor is bored out along an axis of symmetry 12" which passes through its geometric center. A detonator 2i? lits the bore 19 and is held in fixed position therein as by crimping as indicated at 18 and 18a, Figures l and 2. From these figures it will also be noted that rotor 16 has a flat 21 across one end thereof in general parallelism with a diameter of the rotor to receive a straight portion 22 of a rotor safety Spring, subsequently described.

The angled safety position of the spherical rotor is indicated in Figure l wherein the axis 1'7 of the rotor lies at an angle to the longitudinal axis of the fuze such that detonator 2d is entirely out of communication with booster 13 whereby the fuze is rendered safe.

The body l is provided with a radial slot 25 which, as shown, opens through the bore 7 and the outer wall of the body throughout substantially its entire forward portion and at its base communicates with a circumferential groove 24 extending about the base portion of the body.

A rotor safety spring, Figure 4, comprises an annular portion 23 and a straight portion 22 integral therewith and extending upwardly and radially inwardly. As is clear from inspection of the drawing, rthe annular portion 23 seats within groove or channel 24 while the straight portion 22 has a smooth t within slot 2S.

The bias of the spring arm is radially inward toward the longitudinal axis of the fuze body so that it normally seats on flat 21 and holds the rotor in its safety position as shown in Figure 1 and prevents movement thereof within the spherical seat.

The end 26 of the fuze spring normally extends into the bore 7 as clearly shown upon Figure 1. An important feature of the invention is the shape of the end of portion 22 of the spring. Extending downwardly from the flat top end of the spring are two diametrically opposed oblique dat surfaces 27 and 28. The inner flat surface 28 being of substantially greater length than the outer flat surface 27.

Positioned in the bore 7 is a floating substantially cylindrical tiring pin Z9 having a dome-shaped top surface 30. The lower end of the firing pin, as clearly shown .upon Figures 1 and 2 is formed with a circumferential V-shaped channel or groove 32 whose interior periphery merges into a conical downwardly protruding point or pin. 'f he width of the outer frusto-conical portion of the Vshaped channel is substantially the same as the corre sponding dimension of flat surface 27 of spring arm 22 and it will be noted from Figure l that the dimensions and proportions are such that in the safe position the intermediate portion of the arm engages flat 2i to releasably hold rotor 16 in safe position and against rotational movement. At the same time, the end of the arm engages within channel 32 and holds the firing pin 29 forwardly out of Contact with the rotor.

Operation is as follows:

T he normal bias of the rotor safety spring arm 22 tends to maintain the rotor i6 on the spherical seat, as shown in Figure l, thus sealing off the flash passage 14 from the detonator 2f). Forces due to ynormal handling of the ammunition are not capable of deflecting the spring enough to permit the rotor 16 to move morethan a small amount from this position. Furthermore, any temporary displacement of the spring arm under almost any conceivable condition of handling would be followed by prompt return to the holding position shown in Figure 1, without imposition on the rotor of any forces which might rotate it to the armed position.

Upon firing there is both an axial and an angular acceleration upon the projectile as it traverses the barrel. The linear acceleration seats the rotor 16 firmly upon the Vrearward portion of the spherical seat, applies a clockwise movement to the spring arm 22, and urges firing pin 29 :firmly against the end of the arm. This adds to the nor- 'mal inward bias of the spring arm and aids in maintaining the rotor firmly seated upon the spherical seat. The :set back force on the ring pin 29 supplements the clock- A`wise movement on the spring arm by pressing inwardly v'and rearwardly the end 25 of the spring arm seated within channel 32. This force and the shape of the channel 32 :causes the parts to act as an interlock thus preventing the centrifugal force upon thc spring arm from initially movfing it outward to release the firing pin and rotor.

Therefore, as long as axial acceleration continues, that is, as long as the projectile is traversing the bore of the barrel, the rotor is positively held in its safe position as indicated in Figure l.

ln a spring arm having an end of the shape disclosed by the Thompson construction, the set back force sometimes results in the top edge of the spring arm endbeing embedded in the base of the firing pin. This results in a binding between the firing pin and the spring arm. When 'the projectile emerges from the barrel, axial acceleration lceases and deceleration sets in. The firing pin then normally creeps to the top 9 of the drum 8, to the position shown upon Figure 2. However, it' the end of the spring 'arm is embedded in the base of the firing pin this creep- .ing action cannot take place and the spring arm will not be released and in turn will not release the rotor. To obviate this binding the present invention modifies the shape of the outer end of the spring arm so as vto provide Ja flat oblique surface of the same length and obliqueness ras the outer face of the channel 32. With this construc- -tion binding cannot occur and proper functioning is as- ',sured upon impact.

Unlike the Thompson construction, mentioned above, 'the floating firing pin of this invention upon axial deceleration creeps to and presses firmly against the top 9 of the windshield 8 and remains in that position until impact. This action is the result of a constant diameter firing pin riding in a tapered bore rather than in a bore of constant diameter.

Also, impact action causes a slight outward fiow of metal in the portion of the firing pin situated above the bore which results in a slight shoulder being formed about the periphery of the upper portion of the firing pin. If the bore is of a constant diameter substantially the same as the firing pin, as in the Thompson construction, the distortion may extend beyond the edge of the bore to such an extent as to act as a stop, thus preventing proper functioning of the fuze. However, with a tapered bore this possibility is eliminated and there is no impediment to movement of the firing pin toward the detonator.

Although there is enough axial deceleration to cause the fioating ring pin to creep forward to engage the top 9 of the drum as shown in Figure 2, the angular velocity continues high enough so that the centrifugal force bends the spring arm 22 out radially to free the same from the rotor fiat 21. Since the density of the detonator material 2@ is less than the density of the rotor 16, the rotor precesses into the position wherein its maximum moment is aligned with the axis of spin of the projectile which of course is the position shown upon Figure 2 wherein the bore 18 is in line with the flash passage 14 and the detonator is in line with the path of the firing pin.

After the fuze is armed in flight, should the angular velocity drop to a point allowing the spring arm 22 to be biased inwardly and press against the armed rotor 16, the fuze would remain armed since the spring arm would hold the rotor in its armed position. It is to be noted Vthat under such conditions the projectile will be detonated on impact because the spring arm 22 in engaging the spherical surface of the rotor, will be held far enough outwardly so that, on impact, the firing pin will clear the surface 28 of the arm. A

While we have illustrated and described our invention in some detail, it is to be understood that the invention is not to be limited to such details, but only by the spirit of the invention and the scope of the appended claims.

What we claim is:

l. In a fuze, a fuze body having a generally spherical cavity and a forwardly flaring first bore opening into and extending forwardly from said cavity, a generally spherical rotor fitting said cavity and having a diametral bore adapted to receive a detonator and flat across one end normal to and intersecting the axis of said bore, there being a circumferential groove in said body adjacent the rearward portion of said cavity and coaxial with said bore, a firing pin reciprocable in and along said first bore and a safety spring having an annular portion fitting said groove and a straight upwardly extending portion stressed radially inwardly and engaging across said flat to thereby releasably fix said rotor and maintain said diametral bore and first bore out of alignment, the free end of said straight portion received in and engaging a V-shaped slot formed in the lower face of said firing pin to simultaneously maintain the same out of contact with said rotor.

2. In a fuze, a fuze body having a generallyspherical cavity and first and second aligned bores opening into and extending forwardly and rearwardly respectively from said cavity said first bore having a forwardly and outwardly directed taper, a generally spherical rotor fitting said cavity and having a diametral bore adapted to receive a detonator and flat across one end normal to and intersecting the axis of said bore, there being a circumferential groove in said body adjacent the intersection of said cavity and second bore and coaxial with said bore, a firing pin reciprocable in and along said first bore and a safety spring having an annular portion fitting said groove and a straight upwardly extending portion stressed radially inwardly and engaging within said groove to thereby releasably fix said rotor and maintain said diametral bore and second bore out of communication, the free end of said straight portion having diametrically opposed fiat oblique surfaces one of said surfaces engaging a corresponding surface of a V-shaped groove formed in the lower face of said firing pin to simultaneously maintain the same out of contact with said rotor.

3. A fuze comprising a fuze body having forward and rearward axial bores, a booster charge and a detonator housing disposed in said rearward bore, a firing pin having a circumferential V-shaped channel formed in the base thereof, slidably mounted in said forward bore, and latch means for holding said detonator housing in unarmed position comprising a single piece spring member defining an anchoring ring portion adapted to be secured in an annular groove in said fuze body, and an arm portion having a free end adapted to engage said V-shaped channel on said firing pin when said fuze is in unarmed condition, the free end of said spring arm defining a flat oblique surface of the same length and obliqueness as the outer face of said V-shaped channel.

4. A fuze Acomprising a fuze bodyhaving a first rearward axial bore, a booster charge housing and a detonator housing disposed in said rearward bore, there being a second axial bore extending forwardly from and communicating with said first bore, a oating cylindrical 5 firing pin slidable in said second bore, said pin defining at its bases a circumferential V-shaped channel having its interior periphery merging into a conical protruding oblique fiat surfaces, the inner surface being of substantially greater length than said outer fiat surface, and the width of said outer frustroconical portion of said V- shaped channel being substantially equal to the corresponding dimension of said outer flat surface on said free arm of said spring member.

References Cited in the file of this patent UNITED STATES PATENTS Thompson Feb. 3, 1948 2,495,432 Thompson Jan. 24, 1950 2,609,753 Rosenberg Sept. 9, 1952 

